We present an epidemiological and serological study in 286 health care students. We found susceptibility for measles in 11.7% individuals (95% confidence interval (95% CI): 8.0-15%), for rubella: 6.7% (95% CI: 3.8-9.6%) for mumps: 12.7% (95% CI: 8.0-16.6%) and for varicella 8.5% (95% CI: 5.3-11.7%). Compared to a similar study, performed in 1992 in a population of health care workers, we found an increasing susceptibility to these diseases except for mumps, that had decreased. Among those who received one dose of measles vaccine we found 12.1% non immune. We found an high level of immunity (97.1%) for those who received rubella vaccination. We could not draw any conclusions for mumps because only seven had been vaccinated.